Just picked up a ktm sx 125 02, it was a pro action race bike, 1 hour on a new top end and the guy couldnt get it started after it cut out on him, got a four stroke sat in the garge for over a year... now i have it

Took the head off to find the powervalve seized, so lubed it up got it working.

Next i found why it wouldnt start and was lacking compression! The ring was stuck in the groove of the piston! I cant seem to get it out! But the piston still looks perfect, it as if were the ring splits has wedged together..

I will need a new ring.. so i think i will just snap it then see how the piston is!

Hopefully i just need a new ring.

Just wondering why this would happend.. bad ring ends? Or ran in too hot and kinda fryed together?

If the ring gap is under gap spec thermo expansion causes the 2 ends to be smashed together. The expansion further and expands out on the cylinder cause more pressure and heat in essence welding the two ends together.

If it got THAT hot as to fuse the rings ends together, there would be other indicators of heat and friction on the top of the piston and the cylinder walls. That could be true and we just have not seen the pics.

I think something else is up.

Otherwise, I agree with everyone else.
Disassemble completely, put a complete new top end in it and start over. Make sure to check the ring end gap and adjust if it is out of spec.

Since this was a race bike, it's very important that you find out what mods where made to the engine.

Was the bore changed? If so, to what and
Was the compression changed? If it has been bumped up a bit, you better be feeding it race fuel.

The ring is made of fairly hard stuff, I doubt if the metal fused. If the ring end gap was non-existent then it's likely that fuel oil mix has seeped between the ring ends then carbonised due to the heat, this would cause them to be literally cemented together by the hard carbon.

Either way, check that the ring end gap is in spec when you install your new top end...

All I am saying is the expansion without adequate gap will cause the ends to wedge together. He was wondering what was going on here, the only way the 2 could be together is insufficient gap.

Again, agreed.

It's tough to convey tonality in text I guess.

I missed where he mentioned the ends of the ring.

In reading his words literally, I read "stuck in the groove". I was thinking about the stuck power valves and looking for correlating reasons why the ring would be stuck in the groove and went in a direction carbon/foreign matter fusing the ring to itself and the ring land etc.

Truth is, I guess we need more info. Was the ring able to float in the ring land but could not be removed because the ends were fused together? Or.. Was the ring "stuck" in the ring land. 2 different things.

We need pics and info to help him diagnose the problem.

End gap is a likely cause...Agreed. And, it could be other things as well.

Wow, 3 replies before I could get mine in there. Trying to do this while working.

Rocky, show us pics of the head, plug, piston crown and sides of the piston.
In focus in better than close.

The new Wiseco 58mm ring will definitely need to be filed. It typically calls for .004 per 1 inch of bore. a 58mm bore is a hair over 2 1/4 inches. That puts you at about .0105. Since you might have a ring end gap issue, consider going a bit loose for this ring. Maybe .011 or .0115. I went .012 with my first 144 ring just to be sure and I got streaking in my cylinder plating. I don't think that it was due to end gap though.